Louvered screen support member for particulate material

ABSTRACT

Louvered screen support member for particulate material and especially for ceramic catalyst pellets provides increased resistance to bending in one direction by having vanes which define the louver openings torqued from the plane of a metal sheet in such a way that one lip edge of the vane extends above one side of the metal sheet less than the thickness of the sheet and the other lip edge of the vane extends below the opposite side of the metal sheet less than the thickness of the sheet. The vanes are formed by a punching operation so that the lip edge is elliptically curved in the plane of the edge on one side of the sheet so as to prevent the catalyst pellets from becoming uniformly aligned, and straight on the other side so as to define as large an opening between adjacent vanes as possible. Circular segments formed at the ends of the louver openings eliminate localized stress concentrations which could produce fatigue failure under conditions of severe vibration.

United States Patent Wagner 1 June 25, 1974 LOUVERED SCREEN SUPPORTMEMBER FOR PARTICULATE MATERIAL Melvin H. Wagner, Bartlett, 111.

Universal Oil Products Oil Company, Des Plaines, 111.

Filed: Nov. 6, 1972 Appl. No.: 303,908

Related US. Application Data Continuation-in-part of Ser. No. 126,816,March 22, 1971, abandoned.

Inventor:

Assignee:

Warp 98/121 R Mainwal 52/675 X Warp 161/110 Allen 52/675 X PrimaryExaminer-Henry C. Sutherland Assistant Examiner-Carl D. FriedmanAttorney, Agent or Firm.lames R. l-loatson, Jr.; Barry L. Clark; WilliamH. Page, 11

[57] ABSTRACT Louvered screen support member for particulate materialand especially for ceramic catalyst pellets provides increasedresistance to bending in one direction by having vanes which define thelouver openings torqued from the plane of a metal sheet in such a waythat one lip edge of the vane extends above one side of the metal sheetless than the thickness of the sheet and the other lip edge of the vaneextends below the opposite side of the metal sheet less than thethickness of the sheet. The vanes are formed by a punching operation sothat the lip edge is elliptically curved in the plane of the edge on oneside of the sheet so as to prevent the catalyst pellets from becominguniformly aligned, and straight on the other side so as to define aslarge an opening between adjacent vanes as possible. Circular segmentsformed. at the ends of the louver openings eliminate localized stressconcentrations which could produce fatigue failure under conditions ofsevere vibration.

7 Claims, 13 Drawing Figures PAINTED-" sum 1 or 2 Figure Figure 4 Figure6 Figure 5 Figure /0 PAIENTEmuuzsmm SHEET 2 BF 2 Figure BACKGROUND OFTHE INVENTION The present invention relates to an improved louveredscreen support member for supporting particulate material, andespecially, for supporting ceramic, catalyst coated pellets in acatalytic converter, and is a Continuation -in-Part of Ser. No. 126,816,filed Mar. 22, 1971, now abandoned.

It is generally known that a screen member having louver fins or vanesformed integrally with a flat sheet body member provides resistance tobending in the direction along the length of the fins. Screen membersincorporating this principle are widely used for ventilation purposeswhere the fins not only keep out insects and prevent the entry of rainor sunlight but provide a degree of strength which permits very thinmaterial to be used. Prior art examples of such thin, light deflectingand ventilating screens can be found in US Pat. Nos. 2,366,224 and2,430,518 which disclose fins which are struck out of a thin sheet metalbody in such a way as to extend outwardly from both sides of the sheetat a substantial angle.

While thin louvered screens are suitable for ventilation, they would bequite useless as a catalyst support surface in a catalytic converterused to reduce the amount of exhaust pollution emanating from anautomobile or other device utilizing an internal combustion engine. Onegeneral form of catalytic converter con-.

tains loose catalytically coated ceramic pellets which are retained on ascreen surface. Typically, the screen surface has elongated slottedopenings punched out of a flat surface, with the openings being ofsmaller transverse dimension than the diameter of the pellets. To lendrigidity to such flat screens, even in relatively small sizes, such asthose having a diameter of 5 inches, reinforcing ribs have been weldedto the side of the screen which does not contact the catalyst. Thewelded ribs increase the cost, thickness and weight of the screen andreduce its free area. It has been shown that the environment inside acatalytic converter cna be quite brutal to the parts thereof, andparticularly to the support screens which contact the catalyst. When theengine misses, or when it is accelerated, it passes a quantity ofunburned fuel into the converter. As the converter reacts with this fuelit becomes extremely hot, sometimes upwards of 2,000F. In this heatrange, the material of the screens, typically stainless steel, is lessstrong than it is at lower temperatures. It is therefore moresusceptible to fatigue failure arising from even the slightest stressconcentrations such as those in the vicinity of the stiffening ribwelds. The possibility of fatigue failure is especially great due tovibrations when the engine is rapidly accelerating or maintained at ahigh speed. The exhaust stream is always pulsing when it contacts theinlet screen since it is produced by distinct explosions in thecylinders. However, as the engine speed increases and drives moreexhaust gases into the catalyst, the back pressure produced by thecatalyst bed can increase sufficiently so as to cause the screen to tendto move forward and backward at the same pulsing rate as the incominggas stream. Obviously, to have any metal screen survive such anenvironment for a prolonged period requires that the screen be as freeof stress concentrations as possible. It would also be desirable for thescreen to be easily and economically manufacturable, non-abrasive to thefragile catalyst pellets, as open as possible to permit the free flow ofgases through the converter, and shaped so as to minimize blockage ofthe screen openings by the catalyst pellets.

SUMMARY The preceding problems are quite effectively solved by thecatalyst or other particulate material support screen of the presentinvention which comprises a relatively thick sheet of metal, preferablystainless steel, which has a plurality of elongated openings formed bybending portions of its surface. The openings are formed by shearing themetal in short segments along a series of parallel lines andsimultaneously twisting or torqueing the metal segments defined by eachsucceeding adjacent pair of cut lines so as to produce a series ofparallel vanes which, at their centers, are located at about a 30 angleto the plane of the metal sheet. By the use of appropriate cutting andforming members, the edge portions of the vanes which extend outwardfrom the plane of the sheet to form the catalyst pellet engaging side ofthe screen are formed so as to have an elongated, elliptically curvededge profile in the plane of the edge while the edge portions of thevanes which extend outward from the opposite side of the screen have anelongated, straight edge profile in the plane of the edge. The provisionof a curved profile at one edge of the vanes and a straight profile atthe other edge is, for several reasons, of substantial significance inachieving a support screen which will perfonn effectively for anextended period. The elliptically curved edges provide a constantlychanging opening dimension which prevents the catalyst pellets fromassuming a uniform state of repose against the louver opening, thusproviding for optimum passage of gases around the pellets and thencethrough the louver opening. By having a straight edge profile definingone side of a louver opening and a curved edge profile defining theother side, a large opening area can be achieved, for the same vaneangle, than if both edge profiles were curved.

ln forming the louver screen, the tools used to cut and form the louveropenings start cutting at the center of the opening and then cutprogressively toward the ends. This method of gradual generation of theopenings insures that localized stress zones at each end of the lancedopenings will be minimal as compared to the situation where the cuttersare acting along the entire length of the opening at one time.Furthermore, the cutters coact so as to produce smooth, slightly roundedburr-free edges on the catalyst contacting curved profile side of thescreen. The burr-free edges are of course quite desirable since theyprevent damage to the fragile ceramic pellet which contact the screenand which are vibrated against it by road shocks as well as by thecontinual pulsing of the exhaust gases. The burr-free edges alsoeliminate the necessity of deburring the edges, an operation which wouldnot only be expensive but which could introduce tiny points of localizedstress concentration which could result in premature fatigue failure ofthe screen.

In a modification of the invention, the louver openings are formed so asto include a circular segment at each end. The circular segments improvethe resistance of the support screen to fatigue failure by eliminatingthe very small stress concentrations which naturally exist at the endsof the openings despite the progressive forming operation and theminimal torqueing applied to the vanes at their ends.

It is not intended to limit the louvered, particulate matter supportingscreen to a specific type of construction material inasmuch as suchscreens may be formed from various types of deformable metals such assteel, aluminum, brass, copper, galvanized sheet metal, and the like.When the particulate matter to be supported is to be subjected to a hightemperature oxidizing environment, as would be the case with catalystpellets in a catalytic converter, the screen material would obviouslyhave to be able to withstand the temperature.

Since the torqued vanes extend outwardly from each side of the plane ofthe metal sheet, each vane assumes the nature of an angularly positionedrib or beam structure with outer edge portions spaced from its neutralaxis to thereby provide an increase in moment of inertia, or radius ofgyration, thus increasing the resistance of the sheet to bending in thedirection of the length of the louver openings and greatly increasingits ability to carry a given loading in a rectangular configurationwhich has its longest sides parallel to the openings.

As previously mentioned, it is extremely important when the screen is tobe used in an environment subject to vibration that stressconcentrations be reduced. The degree of torqueing of the vanes relativeto the plane of the sheet material is, accordingly, preferably limitedto an angle of about 3035. This rather small angle minimizes theformation of stress concentrations in the metal and forms a cradle-likesupport for the supported pellets or other particulate matter whichprevents them from passing through the louver openings of being abradedby sharp corner portions of the vane edges. To provide maximum strengthand protection for particulate material supported by the screen, thelouvered screen should have a thickness no greater than about threetimes the thickness of the screen material.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a plan view of thenon-particulate matter supporting side of a louvered screen supportmember having torqued vane members defining the louvered openings;

FIGS. 2, 3, and 4 are sectional views through the support member of FIG.1 taken on lines 2-2, 3-3 and 4-4 of FIG. 1 and 4-4 of FIG. 3;

FIGS. 5 and 6 indicate diagrammatically the edge configuration of thetorqued vane members and the louver openings defined thereby, as viewedangularly in accordance with lines 5-5 and 6-6 in FIG. 3;

FIGS. 7 through 10 indicate diagrammatically, and in a step wise manner,a method which may be utilized for forming the torqued vane members andthe resulting louvered sheet wherein the edge or lip portions of thetorqued vanes have one lip edge portion extending above one side of thesheet and a second lip edge portion extending below the other side ofthe sheet;

FIG. 11 is a perspective view of a modified form of louvered sheet shownin contact with representative rows of catalyst pellets;

FIG. 12 is an enlarged sectional view taken on line 12-12 of FIG. 11;and FIG. 13 is an enlarged sectional view taken on line 13-13 of FIG.11.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now particularly toFIGS. 1 through 4, there is indicated a louvered sheet of material 1, asan article of manufacture, which has a plurality of louvers or openings2 that are in turn formed by spaced twisted or torqued vanes or louverpieces 3. As best shown in FIG. 2, 3 and 4, it will be observed thateach fin or louver piece 3 has an edge or lip portion 3' which is raisedabove the face of one side of the sheet material 1 while, at the sametime, an opposing edge or lip portion 3" will be twisted in a manner toextend beyond the face of the opposite side of the sheet material. Itwill also be noted in both FIGS. 2 and 4 that a major portion of thelips or edges 3' will have a relatively straight edge alignment parallelwith the sheet material 1 while with respect to edges or lips 3" thereis a continuous curve providing a maximum distance of the lipportionfrom the sheet material 1 at the zone opposite the center of each louveropening 2.

In view of the differing edges or lips provided for the fins or louveredpieces 3, it will be noticed that in FIG. 5 or the drawing there is asubstantially flat leading edge portion 3' in turn leading into theopening 2 for the louvered sheet 1. At the same time, as shown by FIG.6, upon viewing the louvered sheet 1 from the opposing face, the curvededge of lip portion 3" provides for a curved inlet portion to each ofthe plurality of louver openings 2.

With respect to forming the improved louvered sheet with the torquedform of fins between louvers, there may, of course, be varying methodsfor forming the louvered sheet as an article of manufacture. Forexample, as noted hereinbefore, where the sheet material is of plasticor other moldable composition, the twisting or torqueing of the finmembers 3 may be accomplished by the molding operation or optionally bya cutting and thermosetting operation. On the other hand, where thelouvered screen material is to be supplied from a deformable material,such as of sheet metal, then the method of forming may be in accordancewith the diagrammatic procedure illustrated in FIGS. 7 through 10.Specifically, there is shown diagrammatically in FIGS. 7 and 8 theinitial relative positions of material 1' and an upper cutter member 4and a lower torqueing and forming member 5. Also, as best'shown in FIG.8, there may be utilized holding members 4' on each side of cutter means4 which move with cutter means 4 and additional spring biased holdingmeans 5' on each side of forming means 5 which can move relative to theforming means 5 whereby the sheet material I can be held in place as thecutter means 4 and forming means 5 continue their operations. In FIG. 9of the drawing, there are indicated further movements for both thecutter means 4 and forming means 5, with the cutter means 4 havingpassed through and initially lanced the material 1' prior to the formingmeans 5 passing beyond the face of the material 1'. At the same time, itcan be seen that the sloping faces of cutter means 4 and forming meand 5will provide for forming each fin member 6 as provided by adjacent cutsin the sheet 1'. In a subsequent movement, forming member 5 will bepushed toward an opposing cutter member 4 to complete the twisting andforming of fin member 6 into a desired position. Specifically, as bestshown in FIG. 10 there is shown tne completed passage of forming means 5through the depth of sheet material 1' and after cutter members 4 havemade the initial lancings into the sheet material 1', whereby each ofthe fins or louver pieces 3a will be caused to be twisted and torquedinto the desired angular positions.

Typically, there will be a plurality of louver openings in any onegroup, or in any one row on a sheet, and as a result, there is theutilization of a plurality of adjacent cutter members 4 and a pluralityof opposing forming members 5 as illustrated in part in FIG. of thedrawing. Also typically, as indicated in F lG. 10, there will be anadditional cutter member required at every group of louvers as comparedto the number of forming members 5. In other words, where four louversare to be provided in any one group through a sheet material, there willbe five cutter members 4 and four forming members 5, with the latterbeing in alignment with four of the cutter members.

ln connection with the present drawing, attention is particularlydirected to FIG. 8 wherein there is the illustration of a curved leading4" for the cutter member 4 as compared with a straight edge portion 5"on forming member 5 whereby there will be resulting different formationsto opposing edge portions of a vane and varying inlets to the louveropenings 2 as best shown by the configurations illustrated with respectto FIGS. 5 and 6. It can be readily seen that the cutter member 4 willinitially contact the metal member 1 at a point, rather than along aline, thus progressively cutting and forming the metal from the centerof the opening towards the ends.

Referring to FIG. 11, a modification of the louver screen shown in FIG.I can be seen with the curved or catalyst supporting side uppermost. Thelouvered screen member 10 includes a plurality of louvered openings 12defined by vanes 13 having curved upper end edges 13 and straight lowerend edges 13. The ends 12 of each louver opening 12 are formed in asemi-circular shape, preferably by punching holes in the member 10 priorto torqueing the metal to produce the vanes 12. The openings in the ends12 serve to prevent stress concentrations from arising at the ends ofthe openings 12 due to the slitting and bending of the louver vanes 12relative to the louver sheet material.

Referring to FlGS. 11 though 13, it will be evident that the curved vaneedges 13" which extend up from the support sheet 10 will cooperate withadjacent vane side portions 13" and catalyst pellets l5 resting on thesheet to cradle and support a row a of pellets resting at the inlet toopening 12. The side portions 13" also support a row of pellets b whichis spaced from the opening 12 by the row of pellets a so that thepellets in row b will lie on a curved line. The non-uniform state ofrepose assumed by the row b pellets pennits better flow of exhaust gasesthrough the openings 12 than if the rows of pellets were parallel asthey would be if they rested on the opposite side of the screen 10.

The pellets 15 are shown in FIG. 12 as having a diameter approximately50 percent of the pitch distance or spacing between adjacent vanesegments 13. This size pellet has proved to be quite satisfactoryalthough, pellets may range in size from about 35 percent to 75 percentof the vane pitch and still retain a tangential contact with both thesurfaces 13''. Dotted pellets 15' and 15" illustrate the contactgeometry of smaller and larger particles. Although the pellets areillustrated as uniform spheres, they are actually of slightly obloidshape and of somewhat varying dimensions.

1 claim as my invention:

1. A louvered screen support member for retaining particulate materialhaving a plurality of adjacent, elongated louver type openings therein,said openings being defined by the elongated edges of torqued vanemembers which are integrally attached at their ends to the supportmember and rotationally torqued about an axis in the plane of thesupport member so as to have a longitudinal vane edge extendingoutwardly from each side of the plane of the support member, the vaneedges on one side of the plane of the support member being continuouslycurved away from the plane of the sheet and projecting outwardlytherefrom and the vane edges on the other side of the plane of thesupport member being substantially linear throughout their extent andprojecting outwardly fromthe plane of the sheet.

2. A louvered screen support member in accordance with claim 1 whereinsaid vane members are torqued to a position relative to the plane of thescreen support member by an amount no greater than that which wouldcause any portion of the vane member to be displaced from the plane ofthe screen support member by a distance equal to the thickness of thescreen support member.

3. A louvered screen support member in accordance with claim 2 whereinsaid vane members are torqued to an angle relative to the plane of thescreen support member which is no greater than 34.

4. A louvered screen support member in accordance with claim 1 whereinsaid vane members are spaced from each other by a predetermined pitch,said vane members being sufficiently thick and of such an angle relativeto the plane of the support member so as to be capable of supportingparticulate matter on its first side in a range of diameters betweenabout 35-75 percent of said pitch so that any of such particulate matterwhich is supported by a pair of vanes so as to bridge one of saidopenings will be in contact with a flat planar side surface of one vaneof said pair of vanes and with a flat planar edge portion of the othervane of said pair of vanes.

5. A louvered screen support member in accordance with claim 1 whereinsaid support member includes a semi-circular opening defining the end ofeach of said louver openings.

6. A louvered screen support member in accordance with claim 1 whereinthe maximum width of the louver openings is less than twice thethickness of the vane members.

7. A louvered screen support member in accordance with claim 1 whereinthe maximum width of the louver openings is less than the thickness ofthe vane members.

1. A louvered screen support member for retaining particulate materialhaving a plurality of adjacent, elongated louver type openings therein,said openings being defined by the elongated edges of torqued vanemembers which are integrally attached at their ends to the supportmember and rotationally torqued about an axis in the plane of thesupport member so as to have a longitudinal vane edge extendingoutwardly from each side of the plane of the support member, the vaneedges on one side of the plane of the support member being continuouslycurved away from the plane of the sheet and projecting outwardlytherefrom and the vane edges on the other side of the plane of thesupport member being substantially linear throughout their extent andprojecting outwardly from the plane of the sheet.
 2. A louvered screensupport member in accordance with claim 1 wherein said vane members aretorqued to a position relative to the plane of the screen support memberby an amount no greater than that which would cause any portion of thevane member to be displaced from the plane of the screen support memberby a distance equal to the thickness of the screen support member.
 3. Alouvered screen support member in accordance with claim 2 wherein saidvane members are torqued to an angle relative to the plane of the screensupport member which is no greater than 34*.
 4. A louvered screensupport member in accordance with claim 1 wherein said vane members arespaced from each other by a predetermined pitch, said vane members beingsufficiently thick and of such an angle relative to the plane of thesupport member so as to be capable of supporting particulate matter onits first side in a range of diameters between about 35-75 percent ofsaid pitch so that any of such particulate matter which is supported bya pair of vanes so as to bridge one of said openings will be in contactwith a flat planar side surface of one vane of said pair of vanes andwith a flat planar edge portion of the other vane of said pair of vanes.5. A louvered screen support member in accordance with claim 1 whereinsaid support member includes a semi-circular opening defining the end ofeach of said louver openings.
 6. A louvered screen support member inaccordance with claim 1 wherein the maximum width of the louver openingsis less than twice the thickness of the vane members.
 7. A louveredscreen support member in accordance with claim 1 wherein the maximumwidth of the louver openings is less than the thickness of the vanemembers.